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Molecular detail of the CT quenching site The molecular site of CT quenching in CP29 comprises Z and a strongly coupled chlorophyll pair (A5 and B5). Strongly coupled to each other Zeaxanthin

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Conclusion The primary event of CT quenching in CP29 involves electron transfer Zea to a strongly coupled chlorophyll dimer in the A5- B5 pocket of CP29, rather than from Zea to a monomeric chlorophyll molecule. Controlling the coupling strength between chlorophylls A5 and B5 in CP29 would modulate the reduction potential of the chlorophyll dimer and therefore could be used to switch ON and OFF the CT quenching.